Which results in the Autoptimized CSS for the background-image being broken because the URL is not recognized as such. The bug has been confirmed already and the fix should land in WordPress 4.7.1.

If you’re impacted and can’t wait for 4.7.1 to be released, there are 2 workarounds: 1. simple: disable the “Aggregate inline CSS”-option 2. geeky: use this code snippet to fix the URL before AO has a change to misinterpret it;